The best heads were the 1955 "555" triple buckle castings on which the early Donovan heads were designed. You'd never feel any difference in a daily driver...might see some on the Dyno.
That's debatable. There are flow numbers put the 331/354 truck/industrial heads right up there with the 555 heads........"AS LONG AS" they are upgraded with the 392 size valves. The 392 heads are actually the worst, because rather than make different intakes for the 392, Chrysler made different heads. Since the 392 is a tall deck, the intake ports of the heads had to be extended and have a bad turn in them. A lot of people make the mistake that since they're "392 heads" they gotta be good. They ain't. lol The real ones to stay away from are the 51-53 331 heads with the tiny round exhaust ports. They flat out suck. lol
